Climate models forecast an intensification of the global temperature cycle. However, the mechanisms by which belowground biota respond to global warming remain elusive, especially when climate change interacts with land conversion. To better understand how climate warming affects soil micro-food web components with land conversion, a mesocosm experiment was set up with soil transplants to a temperate gradient region to stimulate climate warming in both cropland and abandoned land (restored following abandonment from cropland). After 8-year of experiment, the soil micro-food web shifted from a bacterial-dominated channel to a fungal-dominated one after land conversion. Climate warming weakened top-down effects in bacterial channel in both land use types. Relative abundance of soil microbes and nematodes changed with climate warming in both land use types. However, nematode diversity and C flux decreased with increasing mean annual temperature only in cropland. Structural equation modeling analysis suggested that the land conversion affected ecosystem multifunction by stimulating nematode abundance, while climate warming affected ecosystem multifunction through diversity and C flow among the soil faunal communities. Our findings indicate that the effects of climate warming on soil micro-food web communities depend on land use types. Therefore, understanding the effects of climate warming and land conversion on soil fauna helps in predicting the effects of long term warming on ecosystem processes.
